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Fat paradox of steatohepatitis

Authors

  • Hidekazu Tsukamoto,

    Corresponding author
    1. USC-UCLA Research Center of ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine of the University of Southern California and
    2. Department of Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
      Professor Hidekazu Tsukamoto, 1333 San Pablo Street, MMR-412, Los Angeles, CA 90033, USA. Email: htsukamo@usc.edu
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  • Hongyun She,

    1. USC-UCLA Research Center of ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine of the University of Southern California and
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  • Saswati Hazra,

    1. USC-UCLA Research Center of ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine of the University of Southern California and
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  • Jason Cheng,

    1. USC-UCLA Research Center of ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine of the University of Southern California and
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  • Jiaohong Wang

    1. USC-UCLA Research Center of ALPD and Cirrhosis and Department of Pathology, Keck School of Medicine of the University of Southern California and
    2. Department of Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, USA
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Professor Hidekazu Tsukamoto, 1333 San Pablo Street, MMR-412, Los Angeles, CA 90033, USA. Email: htsukamo@usc.edu

Abstract

Alcoholic and non-alcoholic steatohepatitis (ASH and NASH) constitute two major types of chronic liver disease with worldwide prevalence and are histologically indistinguishable with shared pathogenetic mechanisms. More importantly, they have synergistic interactions for liver pathology. Comparative studies on ASH and NASH have been hampered by the use of different animal models with confounding variables, particularly those with extreme genetic, toxic, and malnutrition etiologies. The mouse intragastric model circumvents these problems and reproduces the natural course and etiological background of ASH and NASH. Further, our recent work reproduces a profound synergism between the two in the model. Intracellular accumulation of neural lipids is a hallmark biochemical feature of ASH and NASH. Although impaired lipid oxidation and export may contribute to this pathological change, enhanced lipogenic regulation is frequently encountered, as characterized by induction of lipogenic or adipogenic transcription factors (peroxisome proliferator-activated receptor [PPARγ], liver X receptor α[LXRα], sterol-regulatory element-binding protein-1c [SREBP-1c]). In contrast, we have recently defined transdifferentiation of hepatic stellate cells (HSC), a pivotal event in liver fibrogenesis, as an ‘antilipogenic’ or ‘anti-adipogenic’ phenomenon. Thus, there is an apparent paradox between hepatocytes and HSC in steatohepatitis in terms of the outcome of lipogenic regulation. Our recent work suggests that defective insulin signaling in activated HSC may be responsible for this paradox. Further, activated Wnt signaling is implicated in ‘anti-adipogenic’ stellate cell transdifferentiation in liver fibrogenesis.

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